1. Field of the Invention
The present invention relates to a vehicle headlamp that emits a beam by a lamp unit housed inside a lamp body.
2. Prior Art
A vehicle headlamp emits a beam in a predetermined light distribution pattern by means of a lamp unit that includes a light source and a reflector that reflects the light from the light source forward. A xe2x80x9chot zonexe2x80x9d (which is a high luminous intensity area) of the light distribution pattern is formed at an area near the center of the light distribution pattern so as to enhance the visibility of a road ahead of a vehicle.
Under actual vehicle running conditions, however, the vehicle runs not only on a straight road but also on a curved road. Accordingly, it is preferable that, when the vehicle is running on a curved road, the light distribution pattern sufficiently illuminates the road surface slantwise in front of the vehicle. If, however, the entire light distribution pattern is set to face the frontal portion of the curved road, the luminous intensity decreases in the area from the vehicle front direction to the leftward direction on, for example, a right curved road, giving a driver an uneasy feeling.
It is possible to change the light distribution pattern according to the vehicle running conditions. For instance, in Japanese Patent Application Laid-Open (Kokai) No.H01-109603, a pair of auxiliary reflectors are provided between the light source and the reflector, and these auxiliary reflectors are supported so as to swing in a lateral direction with respect to the reflector. The light distribution pattern changes by way of swinging these auxiliary reflectors.
However, in this vehicle headlamp, two auxiliary reflectors are provided at positions closer to the light source than the reflector. As a result, an image of the light source formed by the light reflected by the auxiliary reflectors becomes large, which, in turn, makes the distribution pattern of the emitted light large. As a result, when the auxiliary reflectors swing, the entire shape of the light distribution pattern changes, but the position of the hot zone makes almost no changes. It is, therefore, difficult to sufficiently enhance the visibility of the road surface ahead when the vehicle runs on a curved road.
Accordingly, the object of the present invention is to provide a vehicle headlamp that is formed by housing a lamp unit inside a lamp body and that is capable of emitting a beam in a light distribution pattern that can be changed in response to the vehicle running conditions.
The above object is accomplished by a unique structure for a vehicle headlamp of the present invention; and in the present invention, a pair of reflectors that form the hot zone are provided on both (left and right) sides of a lamp unit main body, and these reflectors are provided so as to swing in the lateral direction with respect to the lamp unit main body.
More specifically, the vehicle headlamp of the present invention comprises a lamp body and a lamp unit. The lamp unit is housed inside the lamp body and emits forward a beam of a predetermined light distribution pattern that has a hot zone. This lamp unit is comprised of a lamp unit main body and a pair of second reflectors. The lamp unit main body includes a light source and a first reflector that supports the light source and reflects the light from the light source forward. The second reflectors are provided on the left and right sides of the lamp unit main body so as to reflect the light entered thereinto from the light source forward and form the hot zone. The lamp unit main body is supported in the lamp body, and the second reflectors are provided so as to swing in a lateral direction with respect to the lamp unit main body.
The structure of the xe2x80x9clamp unit main bodyxe2x80x9d is not specifically limited to a particular lam unit main body. It is, for example, a so-called parabola type lamp unit main body that has a first reflector formed with respect to a paraboloid of revolution or the like. Alternatively, it can be a projector type lamp unit main body. The projector type lamp unit main body used in the present invention is comprised of: a light source disposed in substantially coaxial with an optical axis extending in a longitudinal direction of a vehicle, a first reflector that reflects a light from the light source forward and close to the optical axis, a condensing lens provided in front of the first reflector, and a shade disposed between the condensing lens and the first reflector so as to shield part of the light reflected by the first reflector.
The xe2x80x9clight sourcexe2x80x9d is not specifically limited to a particular light source in the present invention. It can be a discharge light emitting portion of a discharge bulb, or it can be a filament of an incandescent bulb or the like such as a halogen bulb.
The lamp unit main body in the lamp body is fixedly installed. Nonetheless, it is preferable that the supporting the lamp unit main body be supported in a tiltable fashion in a vertical direction and in a lateral direction from a viewpoint of permitting accurate optical axis adjustment. In the present invention, however, the second reflectors that form the hot zone are provided so as to swing in the lateral direction by the lamp unit main body. Thus, it can be designed so that the lamp unit main body is not tiltable in the lateral direction, and this design would not hinder the optical axis adjustment.
As described above, in the vehicle headlamp of the present invention, the lamp unit housed inside the lamp body emits forward a beam of a predetermined light distribution pattern that has a hot zone. In addition, the lamp unit includes the lamp unit main body that has the first reflector and the pair of second reflectors installed on both sides of the lamp unit main body. Furthermore, the lamp unit main body is supported by the lamp body, and each of the second reflectors freely swings in the lateral direction with respect to the lamp unit main body. Accordingly, the present invention provides the operational effects as described below.
Each of the second reflectors is provided so as to swing in the lateral direction with respect to the lamp unit main body; and the position of the hot zone is, by the swing motion of the second reflectors, moved in the lateral direction with the entire shape of the light distribution pattern facing the vehicle front direction.
Accordingly, by way of swinging each of the second reflectors in the lateral direction with respect to the lamp unit main body according to the vehicle running conditions, the light reflected by each of the second reflectors are sufficiently illuminated on the road surface ahead in the vehicle traveling direction when the vehicle is running not only on a straight road but also on a curved road. In addition, since the light reflected by the first reflector keeps its illumination in the vehicle front direction widely at all times, the driver is prevented from feeling unsecured even while driving on a curved road in the dark.
Thus, according to the present invention, the vehicle headlamp formed by housing the lamp unit in the lamp body emits a beam in a light distribution pattern that is variable in response to the vehicle running conditions.
In the above structure, the second reflectors swing in the lateral direction integrally with each other or in conjunction with each other. However, the second reflectors can be designed so as to swing independently. With this design, the light reflected by each of the second reflectors can be directed to any desired direction, which allows more finely controlled light distribution according to the vehicle running conditions.
Furthermore, in the present invention, the positions of the swing axis of respective second reflectors are not particularly fixed. By way of setting the swing axis positions on a perpendicular axis that passes through the point near the light source, the shape of the distribution pattern formed by the light reflected by each of the second reflectors (and thus the shape of the hot zone) is less likely deformed when each of the second reflectors swings in the lateral direction. As a result, a proper beam control is attainable even when the vehicle runs on a curved road.
In addition, in the present invention, each of the second reflectors is supported by the lamp unit main body at two points, the upper and lower portions, of each second reflector. Thus, each of the second reflectors swings in the lateral direction in a state being supported at its upper and lower points. As a result, the accuracy of the swing angle position of each of the second reflectors is enhanced, and the light distribution pattern formed by the light reflected by each of the second reflectors is effectively prevented from being blurred, that would be caused by, for instance, vibrations of the vehicle.
The specific structure of the xe2x80x9clamp unit main bodyxe2x80x9d is not limited as described earlier. It can be of the projector type lamp unit main body in which an opening is formed in each of the right and left sides of the first reflector so as to allow the light from the light source to enter each of the second reflectors.
In other words, with an adoption of the projector type lamp unit main body, a wide solid angle to be used for the first reflector can be secured, which, in turn, makes the light distribution pattern formed by the light reflected by the first reflector brighter. In the projector type lamp unit main body, the light from the light source entering the right and left sides of the first reflector functions little as an effectively reflected light in terms of light distribution performance of the lamp unit main body. Therefore, with the opening formed in each of the right and left sides of the first reflector, the light from the light source enters each of the second reflectors through the opening. As a result, it is possible to obtain a new light reflected by each of the second reflectors, hardly impairing the light distribution performance of the lamp unit main body.